The present disclosure relates generally to semiconductor devices, and more particularly, to semiconductor devices including field-effect transistors of compound semiconductor series.
Field-effect transistors including compound semiconductor layers of GaAs series and so forth have high electron mobility and desirable frequency characteristics, and have been widely used for this reason in the area of high frequency range device applications such as cellular phones and others. In use presently in the range of the high frequency bands, high electron mobility transistors (HEMTs) are adapted as n-channel FETs (field-effect transistors). Among others, pseudomorphic high electron mobility transistors (pseudomorphic HEMTs or PHEMTs) have also been used for realizing even higher electron mobility after tolerating certain degrees of lattice mismatch in the epitaxial growth. In addition, JPHEMT (junction pseudomorphic HEMT) is also used incorporating a p-n junction formed in its gate region (see Japanese Unexamined Patent Application Publication No. 11-150264, for example).
With the recent trend towards higher performance of n-channel FETs, there is also increasing demand for higher integration, which asks for the development of complementary device elements using compound semiconductors.